Syrian and Russian leaders on December 7 rejected pleas from rebel forces and Western powers for a cease-fire and pressed their campaign to retake Aleppo, aiming for a victory they said would "change the course" of the six-year war.

Syrian President Bashar al-Assad in media interviews echoed reports from independent monitors and news media saying government forces appear on the verge of taking full control of the city, Syria's most populous before the war, after years of rebel control in the east.

Rebels are estimated to have lost 75 percent to 80 percent of the territory they once controlled since mid-November, including most recently the Old City. Recapturing Aleppo would represent Assad's most important stride to date toward ending their long-running rebellion.

"Aleppo will completely change the course of the battle in all of Syria," Assad told the Al-Watan newspaper in an interview due to be published on December 8, according to excerpts released to the media.

"It won't mean the end of the war in Syria," he added, "but it will be a huge step toward this end."

Assad said the chances of a cease-fire are "practically nonexistent" at this point.

"The Americans in particular are insisting on demanding a truce, because their terrorist agents are now in a difficult situation," Assad told the newspaper.

Assad described Aleppo as the "last hope" of rebels and their backers "after their failure in the battles of Damascus and Homs," pro-Damascus television Al-Mayadeen reported on December 7.

Rebel groups and six Western powers repeated calls for a cease-fire in the city on December 7, warning of a humanitarian disaster there.

In a joint statement, the United States, Britain, Germany, Italy, France, and Canada also denounced Assad's government and its ally Russia for "their obstruction of humanitarian aid."

Damascus and Moscow have insisted that rebels must agree to leave Aleppo before they will consider a cease-fire.

Tens of thousands of civilians are still trapped in the remaining rebel-held areas of Aleppo.

"The artillery shelling is nonstop," a resident told the AP news agency by messaging service, describing the humanitarian situation as "really tough."

But Assad told Al-Mayadeen that "the decision to liberate all of Syria is taken and Aleppo is part of it."

Assad said he consulted with Russia about his decision to press ahead with the campaign.

"No decision is issued without discussions between the two countries" on a daily basis, he said.

Russia has given Assad crucial military and diplomatic backing throughout the conflict, which began with a forceful government crackdown on pro-democracy protesters in 2011 and erupted into a civil war that has killed more than 250,000 people.

Moscow helped turn the tide of the war in the government's favor with a major campaign of air strikes that began in September 2015 and that Western governments say has mainly targeted rebels rather than Islamic State militants.

Russian Foreign Minister Sergei Lavrov, who accused the United States this week of backing out of a commitment to help arrange an orderly withdrawal of rebel forces from Aleppo, met with U.S. Secretary of State John Kerry on December 7 in Hamburg, Germany.

No breakthrough was announced after the meeting. Kerry said he and Lavrov discussed "the extraordinarily dire situation in Aleppo" and they would "connect" again on December 8.

Lavrov said he affirmed his support for a proposal he said the United States made last week that involved a complete rebel withdrawal from eastern Aleppo -- a plan from which he said the United States has since backed off.

Meanwhile, a top lawmaker in Moscow said the odds are Aleppo will be "fully liberated" by the end of the year.

"I believe Aleppo will be fully liberated in the immediate future, maybe even before the end of the year," Frants Klintsevich, first deputy chairman of Russia's Federation Council Defense and Security Committee, told TASS.

"This will happen regardless of whether an agreement is reached between Russia and the U.S. on letting militants leave the eastern part of the city," he said.